Golf is hard! When your average golfer swings a golf club, he or she may have dramatic variations in his or her golf swing, resulting in numerous off-center hits, which result in diminished performance when compared to a direct center hit. However, in an attempt to make this very difficult game more enjoyable for the average golfer, golf club designers have come up with unique golf club designs that will mitigate the harsh realities of a less than perfect golf swing.
In one early example, U.S. Pat. No. 4,523,759 to Igarashi discloses a perimeter weighted hollow golfing iron having a foam core with an effective hitting area concentrated toward the center of moment in an attempt to help make the game of golf easier. Distributing the weight of a golf club to the perimeter allow the moment of inertia (MOI) of a golf club head to be increased, reducing the undesirable twisting a golf club as it impacts a golf ball.
U.S. Pat. No. 4,809,977 to Doran et al. shows another example of an attempt to increase the moment of inertia of a golf club head by placing additional weights at the heel and toe portion of the golf club head. This increase in the moment of inertia of the golf club head achievable by increased heel and toe weighting could further prevent the golf club from twisting in a heel and toe direction, which mitigates the undesirable effect of sending a golf ball off the intended trajectory.
Although the initial attempts at increasing the forgiveness and playability of a golf club for an average golfer are admirable, it does not take advantage of the extreme forgiveness that can be achievable by utilizing different materials to form different portions of the golf club head. In one example, U.S. Pat. No. 5,885,170 to Takeda shows the advantage of using multi-materials to create more extreme adjustment of the mass properties. More specifically, U.S. Pat. No. 5,885,170 teaches a body having a face formed of one material while a hosel is formed from another material having different specific gravity from that of the head body. U.S. Pat. No. 6,434,811 to Helmstetter et al. shows another example of utilization of multiple materials to improve the performance of a golf club head by providing a golf club head with a weighting system that is incorporated after the entirety of the golf club head has been formed.
More recently, the improvements in incorporating multi-materials into a golf club head have matured significantly by incorporating numerous multiple materials of different characteristics by machining cavities into the golf club head. More specifically, U.S. Pat. No. 7,938,739 to Cole et al. discloses a golf club head with a cavity integral with the golf club head, wherein the cavity extends from the heel region to the toe region; extending along a lower portion of the back face of the golf club head; extends approximately parallel to the strike face; and is approximately symmetrical about a centerline that bisects the golf club head between the heel region and the toe region.
However, as multiple materials are introduced into the golf club after the body has been completed, the tolerances of the interfaces between the different materials could potentially cause undesirable side effects of altering the feel of the golf club head. U.S. Pat. No. 6,095,931 to Hettinger et al. identifies this specific undesirable side effect of sacrifice in the feel by the usage of multiple different components. U.S. Pat. No. 6,095,931 addresses this issue by providing an isolation layer between the golf club head and the main body portion that comprises the striking front section.
U.S. Pat. No. 7,828,674 to Kubota recognizes the severity of this problem by stating that hollow golf club heads having viscoelastic element feels light and hollow to the better golfer, hence they do not prefer such a golf club. U.S. Pat. No. 7,828,674 address the deficiencies of such a multi-material golf club by incorporating a block of magnesium to be embedded and or press-fitted into the recess formed in the metal only to be sealed with a metallic cover.
Despite all of the above attempts to improve the performance of a golf club head all while trying to minimize the sacrifice in feel of a golf club, all of the methodologies require a significant amount of post manufacturing operation that creates cavities and recesses in the club head for the secondary material to be incorporated. These types of secondary operations are not only expensive, but the ability to maintain tight enough tolerances and bonds between the various components makes it very difficult to maintain the solid feel generally associated with an unitarily formed golf club head.
Hence, it can be seen from above, despite all of the development in creating a golf club head that's more forgiving without sacrificing the feel associated with a conventional club head, the current art is incapable of creating such a club without utilizing severe post manufacturing machining that causes bad feel.